This invention relates generally to electron tube bases and particularly to a cathode ray tube (CRT) base which protects the electrical pins, which extend from the tube, from bending during application of the base to the neck of the tube and while the tube is being processed.
CRTs include a neck portion in which the electron beam producing guns are mounted. A coaxial exhaust tubulation extends from a stem that closes the end of the neck. The tubulation is used to evacuate gases from the finished tube. After evacuation, the tubulation is cut off and sealed leaving a tubulation terminus and stem permanently affixed to the neck. The stem, thus, appears as an annular end wall extending between the tubulation terminus and the outer circumference of the neck. A plurality of electrical connector pins extend through the stem and are used to apply the various operating voltages to the electron gun. A hollow, cylindrical, insulative base has a pattern of pinholes in one end. The pinholes receive the connector pins when the base is coaxially applied to the end of the neck portion and about the terminus of the tubulation. Either the outer configuration of the base, or the connector pin pattern is nonsymmetrical. A socket member has a congruent and mating configuration, or pinhole pattern, so that the socket can be coupled to the base in only a particular orientation. The socket includes electrical contacts which engage the connector pins extending through the stem of the neck portion. Because the base and socket can be coupled in only one orientation, each of the electrical contacts within the socket engages a specific connector pin and the proper operating voltages are applied to the various electrodes of the electron gun.
Typically, the tubes must go through many production steps after the electron guns and electrical connector pins are mounted in the neck. However, with prior art bases the exhaust tubulation makes it impossible, or difficult, to apply the base to the tube. For this reason, the pins are unprotected and a substantial number of the pins become bent during the many processing steps. Another problem arises from the fact that when the bases are initially applied to the necks they can not be permanently applied. For this reason, it is necessary to provide a means for temporarily retaining the bases on the necks to permit the occasional removal and reapplication of the bases. A common method of temporarily retaining the bases on the necks is to dimension the connector pins and the pinholes to have an interference fit. Difficulties arise from this technique because the bases are difficult to apply to the necks and bent connector pins frequently result.
For these reasons, there is a need for a base which is easily applied to the neck of the tube and which temporarily retains the base on the neck, and also for a base which can be put onto the pins prior to many of the processing steps, to protect the pins from bending during processing. The present invention fulfills these needs.